Semiconductor device and method of manufacturing semiconductor device

ABSTRACT

A semiconductor device includes a first insulating film formed above a semiconductor substrate, a fuse formed above the first insulating film, a second insulating film formed above the first insulating film and the fuse and including an opening reaching the fuse, and a third insulating film formed above the second insulating film and in the opening.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No.13/606,710, filed Sep. 7, 2012, which is based upon and claims thebenefit of priority of the prior Japanese Patent Application No.2011-194648, filed on Sep. 7, 2011, the entire contents of which areincorporated herein by reference.

FIELD

The embodiments discussed herein are related to a semiconductor deviceincluding a fuse and a method of manufacturing the same.

BACKGROUND

Reconstruction of a semiconductor device, such as characteristicadjustment in an analog circuit, rescue of a defective cell in a memorydevice, etc., are made by mounting in advance a fuse circuit including aplurality of fuses in the semiconductor device and disconnecting thefuses after operational tests, etc. have been made.

The fuses are of the known modes of being disconnected by explosion orsublimation by laser beam irradiation and of being fused by Joule's heatgenerated by current applied to the fuses, and other modes.

The mode of disconnecting the fuse by laser beam irradiation cannot bemade after the package processing and is made in the wafer testing stepbefore the package processing. In the package processing after thesemiconductor device has been reconstructed in the wafer state, oftenthe semiconductor chips are strained by the stress of the package resin,and the strain deviates the adjusted device characteristics.

On the other hand, the mode of fusing the fuse can break the fuse in atest after the packaging, and is suitable for trimming requiring highprecision for, e.g., adjustment of reference potentials of analogproducts, etc.

The followings are examples of related: Japanese Laid-open PatentPublication No. 09-069570; and Japanese Laid-open Patent Publication No.2005-136381.

In the mode of disconnecting the fuse by fusing, current flowed to fusethe fuse and substances around the fuse and then re-solidify the fusedareas to electrically disconnect them, and the fuse cannot be sublimatedas in disconnecting the fuse by laser beam irradiation. Consequently,depending on structures around the fuse and states of the re-solidifiedareas, the degree of the electric disconnection is not alwayssufficient.

SUMMARY

According to one aspect of an embodiment, there is provided asemiconductor device including a first insulating film formed above asemiconductor substrate, a fuse formed above the first insulating film,a second insulating film formed above the first insulating film and thefuse and including an opening reaching the fuse, and a third insulatingfilm formed above the second insulating film and in the opening.

According to another aspect of an embodiment, there is provided a methodof manufacturing a semiconductor device including forming a firstinsulating film above a semiconductor substrate, forming a fuse abovethe first insulating film, forming a second insulating film above thefuse and the first insulating film, forming an opening in the secondinsulating film to expose the fuse, and forming a third insulating filmabove the second insulating film and in the opening.

According to further another aspect of an embodiment, there is provideda method of manufacturing a semiconductor device including forming afirst insulating film above a semiconductor substrate, forming a fuseabove the first insulating film, forming a second insulating film incontact with the first insulating film above the semiconductor substratewith the fuse formed on, forming a third insulating film above thesecond insulating film, forming an opening in the second insulating filmand the third insulating film above the fuse, and forming in the openinga fourth insulating film formed of an insulating material whose meltingpoint is lower than a melting point of the third insulating film.

The object and advantages of the embodiment will be realized andattained by means of the elements and combinations particularly pointedout in the claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and arenot restrictive of the embodiments, as claimed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view illustrating a structure of a semiconductor deviceaccording to a first embodiment;

FIGS. 2 and 3 are diagrammatic cross-sectional views illustrating thestructure of the semiconductor device according to the first embodiment;

FIGS. 4A and 4B are views illustrating a problem with an etching stopperfilm present on a fuse;

FIGS. 5A-5K, 6A-6H and 7A-7I are cross-sectional views illustrating amethod of manufacturing the semiconductor device according to the firstembodiment;

FIG. 8 is a diagrammatic cross-sectional view illustrating a structureof a semiconductor device according to a second embodiment;

FIGS. 9A-9C are cross-sectional views illustrating a method ofmanufacturing the semiconductor device according to the secondembodiment;

FIG. 10 is a diagrammatic cross-sectional view illustrating a structureof a semiconductor device according to a third embodiment; and

FIGS. 11A-11B are cross-sectional views illustrating a method ofmanufacturing the semiconductor device according to the thirdembodiment.

DESCRIPTION OF EMBODIMENTS A First Embodiment

A semiconductor device and a method of manufacturing the semiconductordevice according to a first embodiment will be described with referenceto FIGS. 1 to 7I.

FIG. 1 is a plan view illustrating a structure of the semiconductordevice according to the present embodiment. FIGS. 2 and 3 arediagrammatic cross-sectional views illustrating the structure of thesemiconductor device according to the present embodiment. FIGS. 4A-4Bare views illustrating a problem with an etching stopper film present ona fuse. FIGS. 5A-5K, 6A-6H and 7A-7I are cross-sectional viewsillustrating a method of manufacturing the semiconductor deviceaccording to the present embodiment.

First, the structure of the semiconductor device according to thepresent embodiment will be described with reference to FIGS. 1 to 3.FIG. 2 is the A-A′ line cross-sectional views of FIG. 1, and FIG. 3 isthe B-B′ line cross-sectional view of FIG. 1.

A device isolation insulating film 12 is formed in a silicon substrate10. A fuse 16 of polycrystalline silicon is formed above the deviceisolation insulating film 12. As illustrated in FIG. 1, the fuse 16 hasa plane shape narrowed at the intermediate part. On both sides of thefuse 16, dummy interconnections 18 for preventing damages from spreadingwhen the fuse 16 is fused. A metal silicide film 36 is formed above thesurfaces of both ends of the fuse 16 and above the dummyinterconnections 18. Silicon oxide films 22, 26 are formed above theregion of the fuse 16, where the metal silicide film 36 is not formed.

An etching stopper film 38 and an inter-layer insulating film 42 areformed above the device isolation insulating film 12 with the fuse 16and the dummy interconnections 18 formed on. Contact plugs 46 connectedto the metal silicide film 36 are buried in the inter-layer insulatingfilm 42 and the etching stopper film 36. Interconnection layers 48connected to the contact plugs 46 are formed above the inter-layerinsulating film 42.

An inter-layer insulating film 50 is formed above the inter-layerinsulating film 42 with the interconnection layers 48 formed on. Contactplugs 52 connected to the interconnection layers 48 are buried in theinter-layer insulating film 50. Interconnection layers 54 connected tothe contact plugs 52 are formed above the inter-layer insulating film50.

An inter-layer insulating film 56 is formed above the inter-layerinsulating film 50 with the interconnection layers 54 formed on. Contactplugs 58 connected to the interconnection layers 54 are buried in theinter-layer insulating film 56. Interconnection layers 60 connected tothe contact plugs 58 are formed above the inter-layer insulating film56.

A silicon oxide film 62 and a silicon nitride film 64 as a cover filmare formed above the inter-layer insulating film 56 with theinterconnection layers 60 formed on.

In the semiconductor device according to the present embodiment, asillustrated in FIGS. 2 and 3, the etching stopper film 38 is absentabove the fuse 16. The reason for the etching stopper film 38 beingabsent above the fuse 16 in the semiconductor device according to thepresent embodiment will be described below.

Below an inter-layer insulating film of a semiconductor device, anetching stopper film of etching characteristics different from those ofthe inter-layer insulating film is often formed. For example, whencontact holes of different depths are concurrently formed in theinter-layer insulating film, the region for the shallow contact hole tobe formed in is exposed to excessive etching, and the structure at thebottom of the contact hole is often damaged. Then, the etching stopperfilm of etching characteristics different from those of the inter-layerinsulating film is provided to thereby protect the base structure fromthe etching damage.

As the inter-layer insulating film, an insulating material mainly formedof silicon oxide such as silicon oxide film or others is widely used.When the inter-layer insulating film is formed of an insulating materialmainly formed of silicon oxide, an insulating material mainly formed ofsilicon nitride, such as silicon nitride film or others is widely usedas the etching stopper film for stopping the etching of the inter-layerinsulating film.

However, the inventor has made studies and found that with the etchingstopper film 38 present above the fuse 16, the fuse 16 cannot be fusedstably with a good disconnection degree. The inventor infers that thereason why the fuse 16 cannot be fused stably is as follows.

For a semiconductor device in which trimming and redundancy are madeafter package processing, as described above, preferably the fuse 16 isdisconnected by flowing current to the fuse 16. Such fuse 16 has theconfiguration having the intermediate part narrowed as exemplified inFIG. 1. When current is flowed to such fuse 16, the temperature risesdue to the Joule's heat at the intermediate part where the currentdensity goes up, and the fuse 16 and the its surrounding materials arefused. Due to the fusing of the fuse 16, the current stops flowing. Thetemperature goes down, and the fused part is re-solidified.

Here, the case that, as exemplified in FIG. 4A, the etching stopper film38 of the silicon nitride film is present above the fuse 16 is assumed.Silicon nitride film of the etching stopper film 38 has a large stressapplied to the silicon substrate 10 in comparison with silicon oxidefilm forming the inter-layer insulating films between theinterconnection layers, and the device isolation insulating film 12.With the etching stopper film 38 of silicon nitride film present abovethe fuse 16, a compressive stress is applied to the fuse 16 from theetching stopper film 38 toward the silicon substrate 10.

When the fuse 16 is disconnected in this state, the stress applied bythe etching stopper film 38 suppresses the effect of increase of thevolume by fusing the fuse 16 and its surroundings. Resultantly, thefused region 70 is made smaller, and the gaps between the fragments ofthe polycrystalline silicon, the fuse material, which are re-solidified,becomes small, and the electric disconnection degree is worsened (referto FIG. 4B). The decrease of the fused region 70 might be also due tothe higher melting point of silicon nitride than that of silicon oxide.

From this view point, in the semiconductor device according to thepresent embodiment, the etching stopper film 38 above the fuse 16 isselectively removed. The etching stopper film 38 above the fuse 16 isremoved, whereby the fused region 70 can be widened without theinfluence of a stress from the etching stopper film 38. Thus, the fuse16 can be fused stably with a good disconnection degree.

It is not necessary to remove the etching stopper film 38 from theentire surface of the fuse 16. The etching stopper film 38 is removed atleast from the part of the fuse 16, where the fuse 16 is fused when thefuse 16 is disconnected, i.e., the narrowed part of the fuse 16, whichis at the intermediate part of the fuse 16.

Next, a method of manufacturing the semiconductor device according tothe present embodiment will be described with reference to FIGS. 5A to7I. FIGS. 5A to 5K are the A-A′ line cross-sectional views of thesemiconductor device in the steps of the semiconductor devicemanufacturing method. FIGS. 6A to 6H are B-B′ line cross-sectional viewsof the semiconductor device in the steps of the semiconductor devicemanufacturing method. FIGS. 7A to 7I are sectional views of thesemiconductor device in the steps of the semiconductor devicemanufacturing method in the transistor forming region.

First, the device isolation insulating film 12 defining active regionsis formed in the silicon substrate 10 by, e.g., LOCOS (LOCal Oxidationof Silicon) method. The device isolation insulating film 12 is so formedhere that the fuse 16 is formed above the device isolation insulatingfilm 12 (FIGS. 5A, 6A and 7A). The device isolation insulating film 12may be formed by STI (Shallow Trench Isolation) method.

Then, above the active region of the silicon substrate 10 defined by thedevice isolation insulating film 12, a gate insulating film 14 of, e.g.,silicon oxide film is formed by, e.g., thermal oxidation method.

Next, a polycrystalline silicon film and a silicon oxide film aresequentially formed above the entire surface by, e.g., CVD (chemicalvapor deposition) method.

Then, by photolithography and dry etching, the silicon oxide film andthe polycrystalline silicon film are patterned to form the fuse 16, thedummy interconnections 18 and a gate electrode 20 which have the uppersurfaces covered by the silicon oxide film 22.

Then, ion implantation is made with the gate electrode 20 as the mask toform impurity diffused regions 24 to be the LDD regions or the extensionregions in the silicon substrate 10 on both sides of the gate electrode20 (FIGS. 5B, 6B and 7B).

The silicon oxide film 22 is to be used to prevent the silicidation in alater step. In forming the metal silicide film 36 above the entire uppersurface of the gate electrode 20, when the metal silicide film 36 is notused, it is not essential to form the silicon oxide film 22. When thesilicon oxide film 22 is not formed, a silicon oxide film 26 to beformed in a later step can be used to block the silicidation of theregion of the fuse 16.

Next, a silicon oxide film 26 is formed above the entire surface by,e.g., CVD method.

Then, by photolithography, a photoresist film 28 covering the fuse 16and exposing the rest region is formed (FIGS. 5C, 6C and 7C).

Next, with the photoresist film 28 as the mask, the silicon oxide film26 is anisotropically etched to be left, covering the fuse 16 whileforming sidewall insulating films 30 thereof on the side walls of thedummy interconnections 18 and the gate electrode 20.

Next, the photoresist film 28 is removed by, e.g., asking method.

Then, with the gate electrode 20 and the sidewall insulating film 30 asthe mask, ion implantation is made to from impurity diffused regions 32in the silicon substrate 10 on both side of the gate electrode 20. Thus,source/drain regions 34 including the impurity diffused regions 24, 32are formed (FIGS. 5D and 7D).

Then, by photolithography and dry etching, the silicon oxide films 22,26 are patterned to expose the silicide forming regions of the fuse 16,dummy interconnections 18 and the gate electrode 20 (FIGS. 5E, 6D and7E). In the fuse 16 and the dummy interconnections 18, contact regionswhich connect interconnection layers to be connected to the fuse 16 andthe dummy interconnections 18 are exposed.

Next, the metal silicide film 36 is formed by salicide (self-alignedsilicide) process as required selectively in the exposed parts of thefuse 16, the dummy interconnections 18 and gate electrode 20 (FIGS. 5F,6E and 7F). At this time, the silicon oxide films 22, 26 formed abovethe fuse 16 function as the silicide block insulating film.

Then, a silicon nitride film is deposited above the entire surface by,e.g., CVD method to form the etching stopper film 38 of silicon nitridefilm (FIGS. 5G and 7G). The etching stopper film 38 is a film whichmitigates etching damage to be applied to the base and is formedordinarily in contact with the base to be protected from etching (e.g.,the device isolation insulating film 12, the gate electrode 20 includingthe metal silicide film 36, the source/drain regions 34, etc.).

Next, by photolithography, a photoresist film 40 exposing the region forthe fuse 16 formed in, at least the region containing the region wherethe fuse 16 will be fused and covering the rest region is formed.

Then, with the photoresist film 40 as the mask and with the etchingstopper film 38 as the stopper, the etching stopper film 38 is dryetched to form an opening in the etching stopper film 38 above the fuse16 (FIGS. 5H and 6F).

The etching stopper film 38 is etched here with the silicon oxide film26 as the stopper but cannot be etched essentially with the siliconoxide film 26 are the stopper. When the silicon oxide film 22 is usedfor the silicide block for the fuse 16 or the metal silicide film is notused, the silicon oxide film 26 is not essentially formed.

Next, the photoresist film 40 is removed by, e.g., asking method.

Then, a silicon oxide film is deposited above the entire surface by,e.g., CVD method to form the inter-layer insulating film 42 of siliconoxide film (FIGS. 5I and 7H).

Next, by photolithography and dry etching, the contact holes 44 down tothe metal silicide film 36 on the fuse 16, the dummy interconnections18, the gate electrode 20 and the source/drain regions 34 are formed inthe inter-layer insulating film 42 and the etching stopper film 38.

At this time, the contact hole 44 opened above the gate electrode 20 andthe contact holes 44 opened above the source/drain regions 34 havedepths different from each other, but the etching stopper film 38 belowthe inter-layer insulating film 42 can prevents the gate electrode 20from being exposed to excessive etching.

Then, a conductive film is deposited above the entire surface, and theconductive film is etched back to form the contact plugs 46 buried inthe contact holes 44.

Next, a conductive film is deposited above the inter-layer insulatingfilm 42 with the contact plugs 46 buried in, and the conductive film ispatterned. Thus, the interconnection layers 48 electrically connected tothe fuse 16, the dummy interconnections 18, the gate electrode and thesource/drain regions 34 via the contact plugs 46 are formed (FIGS. 5J,6G and 7I).

Next, in the same way, the inter-layer insulating film 50, the contactplugs 52, the interconnection layers 54, the inter-layer insulating film56 the contact plugs 58 and the interconnection layers 60 aresequentially formed, and the interconnection layer structure of arequired layer number is formed.

Then, above the inter-layer insulating film 56 with the interconnectionlayers 60 formed on, a silicon oxide film 62 and a silicon nitride film64 as a cover film are formed, and a string of wafer processes iscompleted (FIGS. 5K and 6H).

Next, the semiconductor substrate 10 which has been subjected to theabove-described string of wafer processes is subjected to dicing andpackaged.

Next, a circuit test is made on the packaged semiconductor device todetect whether required circuit characteristics have been provided. Whenthe required circuit characteristics have not been provided, requiredfuses are disconnected for trimming or redundancy.

In the semiconductor device according to the present embodiment, theetching stopper film 38 above the fuse has been removed, whereby thefuse can be stably and surely disconnected. The circuit test and thetrimming are made after packaged, whereby even when devicecharacteristics have been deviated due to a stress of the package resin,the trimming of high precision including the deviation can be made, anda semiconductor device having a small characteristic deviation can bemanufactured.

As described above, according to the present embodiment, the etchingstopper film above the fuse is removed, the fuse of the fusing mode canbe stably and surely disconnected. The circuit test and the trimming aremade after packaged, whereby even when device characteristics have beendeviated due to a stress of the package resin, the trimming of highprecision including the deviation can be made, and a semiconductordevice having a small characteristic deviation can be manufactured.

A Second Embodiment

A semiconductor device and a method of manufacturing the semiconductordevice according to a second embodiment will be described with referenceto FIGS. 8 to 9C. The same members of the present embodiment as those ofthe semiconductor device and the method of manufacturing the sameaccording to the first embodiment illustrated in FIGS. 1 to 7I arerepresented by the same reference numbers not to repeat or to simplifythe description.

FIG. 15 is a cross-sectional view illustrating a structure of thesemiconductor device according to the present embodiment. FIGS. 9A-9Care cross-sectional views illustrating the method of manufacturing thesemiconductor device according to the present embodiment.

First, the structure of the semiconductor device according to thepresent embodiment will be described with reference to FIG. 8.

In the semiconductor device according to the present embodiment, asillustrated in FIG. 8, the etching stopper film 38 above the fuse 16 isremoved, and the inter-layer insulating film 42 in the region where theetching stopper film 38 is removed is replaced by a low melting pointinsulating film 82 of an insulating material having a lower meltingpoint than the inter-layer insulating film 42.

The low melting point insulating film 82 whose melting point is lowerthan the melting point of the inter-layer insulating film 42 is formedaround the fuse 16, whereby the fusion upon a disconnection of the fusetakes place in a wider area, and the electric disconnection degree canbe further improved.

The material of the low melting point insulating film 82 is notspecifically limited as long as the melting point of the material islower than that of the inter-layer insulating film 42. For example,silicon oxide containing impurity, such as BPSG, PSG, BSG, AsAG, etc.,spin-on type insulating material, such as SOG or others can be used.

Next, the method of manufacturing the semiconductor device according tothe present embodiment will be described with reference to FIGS. 9A-9C.

First, in the same way as in the method of manufacturing thesemiconductor device according to the first embodiment as exemplified inFIGS. 5A to 5G, the structure up to the etching stopper film 38 isformed.

Then, above the etching stopper film 38, a silicon oxide film isdeposited by, e.g., CVD method to form the inter-layer insulating film42 of silicon oxide film (FIG. 9A).

Next, a photoresist film 40 exposing the region for the fuse 16 formedin, at least the region containing the region where the fuse 16 will befused and covering the rest region is formed above the inter-layerinsulating film 42 by photolithography.

Then, with the photoresist film 40 as the mask, the inter-layerinsulating film 42 and the etching stopper film 38 are dry etched toform an opening 80 in the etching stopper film 38 and the inter-layerinsulating film 42 (FIG. 9B). The opening 80 can be formed also in thesilicon oxide film 26 by etching the silicon oxide film 26 with thephotoresist film 40 as the mask.

Next, the photoresist film 40 is removed by, e.g., asking method.

Then, a BPSG film, for example, is deposited above the entire surfaceby, e.g., CVD method to form the low melting point insulating film 62 onthe inter-layer insulating film 42.

Next, the low melting point insulating film 82 above the inter-layerinsulating film 42 is removed by etching back or CMP (chemicalmechanical polishing) method to be left selectively in the opening 80(FIG. 9C).

Hereafter, in the same way as in the method of manufacturing thesemiconductor device according to the first embodiment as exemplified inFIGS. 5J to 5K, the interconnection layers, the cover film, etc. areformed, and the semiconductor device is completed.

As described above, according to the present embodiment, the etchingstopper film above the fuse is removed, whereby the fuse of the fusingmode can be disconnected stably and surely. Especially, the insulatingmaterial of a melting point lower than that of the inter-layerinsulating film is formed around the fuse, whereby the fused region canbe further widened, and the fuse can be disconnected more stably andsurely.

A Third Embodiment

A semiconductor device and a method of manufacturing the semiconductordevice according to a third embodiment will be described with referenceto FIGS. 10 to 11C. The same members of the present embodiment as thoseof the semiconductor device and the method of manufacturing the sameaccording to the first and the second embodiments illustrated in FIGS. 1to 9C are represented by the same reference numbers not to repeat or tosimplify the description.

FIG. 10 is a diagrammatic cross-sectional view illustrating a structureof the semiconductor device according to the present embodiment. FIGS.11A-11C are cross-sectional views illustrating the method ofmanufacturing the semiconductor device according to the presentembodiment.

First, the structure of the semiconductor device according to thepresent embodiment will be described with reference to FIG. 10.

In the semiconductor device according to the present embodiment, asillustrated in FIG. 10, the etching stopper film 38 above the fuse 16 isremoved, and the silicon oxide films 22, 26, the inter-layer insulatingfilm 42 and the device isolation insulating film 12 around the fuse 16are replaced by the low melting point insulating film of a lower meltingpoint insulating material. Gaps 84 are defined between the deviceisolation insulating film 12 and the low melting point insulating film82 below the fuse 16.

The low melting point insulating film 82 whose melting point is lowerthan those of the silicon oxide films 22, 26, the inter-layer insulatingfilm 42 and the device isolation insulating film 12 is formed around thefuse 16, whereby the fused region upon a disconnection of the fuse 16 isfurther widened, and the electric disconnection degree can be furtherimproved.

Because of the gaps 84, when the fuse 16 is disconnected, thepolycrystalline silicon forming the fuse 16 can diffuse into the gaps84, whereby the ability of the disconnection can be further improved.

Next, the method of manufacturing the semiconductor device according tothe present embodiment will be describe with reference to FIGS. 11A to11C.

First, in the same way as in the method of manufacturing thesemiconductor device according to the second embodiment illustrated inFIGS. 9A to 9B, a photoresist film 40 exposing the region for the fuse16 formed in is formed above the inter-layer insulating film 42.

Next, with the photoresist film 40 as the mask, the inter-layerinsulating film 42 and the etching stopper film 38 are dry etched toform the opening 80 down to the inter-layer insulating film 42.

Next, with the photoresist film 40 as the mask, the silicon oxide films26, 22 and the device isolation insulating film 12 are etched byisotropic etching having selectivity to the material of the fuse 16,e.g., wet etching using, e.g., hydrofluoric acid aqueous solution. Thus,the opening 80 turning in below the fuse 16 is formed (FIG. 11A).

Next, the photoresist film 40 is removed by, e.g., asking method.

Then, a BPSG film, for example, is deposited above the entire surfaceby, e.g., CVD method to form the low melting point insulating film 82 ofBPSG. At this time, because of the fuse 16 extending in the opening 80in the shape of eaves, the regions below the fuse 16 are not completelyburied by the low melting point insulating film 82, and the gaps 84remain.

Next, the low melting point insulating film 82 above the inter-layerinsulating film 42 is removed by etching back or CMP method to leave thelow melting point insulating film 82 in the opening 80 (FIG. 11B).

Hereafter, in the same way as in the method of manufacturing thesemiconductor device according to the first embodiment exemplified inFIGS. 5J to 5K, the interconnection layers, the cover film, etc. areformed, and the semiconductor device is completed.

As described above, according to the present embodiment, the etchingstopper film above the fuse is removed, whereby the fuse of the fusingmode can be stable and surely broken. Especially, the gaps are providedaround the fuse, whereby the fused region can be easily widened, and thefuse can be disconnected further stably and surely.

Modified Embodiments

The above-described embodiments can cover other various modifications.

For example, in the above-described embodiments, the fuse 16 is formedof the gate electrode layer but cannot be essentially formed of the gateelectrode layer. The fuse 16 can be formed of the polycrystallinesilicon layer or others which are above the gate electrode layer.

In the above-described embodiments, the etching stopper film is formedof, e.g., silicon nitride based insulating materials. It is notessential that the etching stopper film is formed of a silicon nitridebased insulating material. The advantageous effect of theabove-described embodiments can be expected in cases that the etchingstopper film is formed of a material which applies a larger stress tothe silicon substrate than the other inter-layer insulating films or theetching stopper film is formed of a material whose melting point ishigher than those of the other inter-layer insulating films.

In the third embodiment described above, the low melting pointinsulating film 82 is formed, leaving the gaps 84 in the regions belowthe fuse 16, but it is not essential to leave the gaps 84. The lowmelting point insulating film 82 is formed, merely surrounding the fuse16, whereby the fused region upon a disconnection of the fuse 16 isextended in a wide area, and the electric disconnection degree can befurther improved.

In the third embodiment described above, the low melting pointinsulating film 82 is formed, leaving the gaps 84 in the regions belowthe fuse 16, but the ordinary silicon oxide film in place of the lowmelting point insulating film 82 may be buried in. The gaps 84 aremerely formed below the fuse 16, whereby when the fuse 16 isdisconnected, the polycrystalline silicon forming the fuse 16 candiffuses also in the gaps 84, and the ability of the disconnection canbe improved.

The structures, the constituent material, manufacturing conditions, etc.described in the above embodiments are only one example and can bemodified or changed suitably in accordance with common sense, etc. ofthose skilled in the art.

All examples and conditional language recited herein are intended forpedagogical purposes to aid the reader in understanding the inventionand the concepts contributed by the inventor to furthering the art, andare to be construed as being without limitation to such specificallyrecited examples and conditions, nor does the organization of suchexamples in the specification relate to a showing of the superiority andinferiority of the invention. Although the embodiments of the presentinventions have been described in detail, it should be understood thatthe various changes, substitutions, and alterations could be made heretowithout departing from the spirit and scope of the invention.

What is claimed is:
 1. A method of manufacturing a semiconductor devicecomprising: forming a first insulating film above a semiconductorsubstrate; forming a fuse above the first insulating film; forming asecond insulating film above the fuse and the first insulating film;forming an opening in the second insulating film to expose the fuse; andforming a third insulating film above the second insulating film and inthe opening.
 2. The method of manufacturing a semiconductor deviceaccording to claim 1, wherein a melting point of the third insulatingfilm is lower than a melting point of the second insulating film.
 3. Themethod of manufacturing a semiconductor device according to claim 1,wherein a stress the second insulating film applies to the semiconductorsubstrate is larger than a stress the first insulating film and thethird insulating film apply to the semiconductor substrate.
 4. Themethod of manufacturing a semiconductor device according to claim 1,wherein the second insulating film is an etching stopper film, and thethird insulating film is an inter-layer insulating film.
 5. The methodof manufacturing a semiconductor device according to claim 1, whereinthe second insulating film is formed of an insulating material mainlyformed of silicon nitride, and the third insulating film is formed of aninsulating material mainly formed of silicon oxide.
 6. A method ofmanufacturing a semiconductor device comprising: forming a firstinsulating film above a semiconductor substrate; forming a fuse abovethe first insulating film; forming a second insulating film in contactwith the first insulating film above the semiconductor substrate withthe fuse formed on; forming a third insulating film above the secondinsulating film; forming an opening in the second insulating film andthe third insulating film above the fuse; and forming in the opening afourth insulating film formed of an insulating material whose meltingpoint is lower than a melting point of the third insulating film.
 7. Themethod of manufacturing a semiconductor device according to claim 6,wherein the fourth insulating film is formed of silicon oxide containingimpurity, or SOG.
 8. The method of manufacturing a semiconductor deviceaccording to claim 6, wherein in forming the opening, the opening isformed in the second insulating film and the third insulating film, andthen the first insulating film is isotropically etched to expose anunderside of the fuse in the opening.
 9. The method of manufacturing asemiconductor device according to claim 6, wherein in forming the fourthinsulating film, the fourth insulating film is formed, leaving a gapbelow the fuse.
 10. The method of manufacturing a semiconductor deviceaccording to claim 6, wherein a stress the second insulating filmapplies to the semiconductor substrate is larger than a stress the firstinsulating film and the third insulating film apply to the semiconductorsubstrate.
 11. The method of manufacturing a semiconductor deviceaccording to claim 6, wherein the second insulating film is an etchingstopper film, and the third insulating film is an inter-layer insulatingfilm.
 12. The method of manufacturing a semiconductor device accordingto claim 6, wherein the second insulating film is formed of aninsulating material mainly formed of silicon nitride, and the thirdinsulating film is formed of an insulating material mainly formed ofsilicon oxide.